This invention relates in general to substrates having indicia imprinted thereon for read-out by infrared scanning apparatus and relates more particularly to improved methods for making coded envelopes, flexible packages, and the like printed in color and adapted for identification and/or sorting at some future time by infrared scanning apparatus.
Heretofore, methods for making envelopes, flexible packages and other items having coded information imprinted thereon for read-out by infrared scanning apparatus utilized inks which contain, as necessary ingredient, carbon black and which, as a result, were either black or of a dull hue. Where ink of a color other than black has been employed, the graduation of color has been generally determined by the concentration of carbon black pigment incorporated in the ink to provide required contrast between the printed area and the substrate. When brightly colored printing and/or printed designs were desired, as for advertising purposes, it has generally been necessary to employ printing apparatus provided with multiple printing stations. More specifically, a printing press has been required which includes one or more stations for imprinting the brightly colored materials and at least one additional station for imprinting the coded material in black or at least a dull color. The limitations imposed by the required black or dull color of the coded material detracted from the aesthetic quality of the finished product, had a detrimental effect on customer acceptance, and thereby reduced the market for such items.
Accordingly, it is the general aim of the present invention to provide improved printing materials wherein brightly colored inks are utilized in the printing process compatible with the requirements of infrared scanning apparatus used to process the item.